Multilayer ceramic capacitor

This application claims the benefit of priority to Japanese Patent Application No. 2024-043985 filed on Mar. 19, 2024. The entire contents of this application are hereby incorporated herein by reference.

The present invention relates to multilayer ceramic capacitors.

For example, the multilayer ceramic capacitor described in Japanese Unexamined Patent Application Publication No. 2001-237137 includes a capacitor body of a ceramic sintered body made of a dielectric material such as barium titanate. Such a capacitor body includes internal electrode layers each made of a noble metal material such as silver or a silver-palladium alloy, or a base metal material such as nickel with a ceramic layer functioning as a dielectric layer interposed therebetween. The internal electrode layers alternately extend toward one end surface and the other end surface of the capacitor body. The internal electrode layers extending toward the one end surface and the internal electrode layers extending toward the other end surface are electrically connected to respective one of external electrodes having different potentials.

The internal electrode layers of the multilayer capacitor described in Japanese Unexamined Patent Application Publication No. 2001-237137 are each made of a metal material, and the external electrodes are each made of a plurality of metal components including the same metal as that of the internal electrode layers or a metal capable of being alloyed with the metal of the internal electrode layers, and a glass component. The external electrodes are each bonded to a wiring board via an electrically conductive resin adhesive. The area occupation ratio of the metal component to the cross-sectional area of each of the external electrodes ranges from 60% to 95%. Thus, the multilayer capacitor described in Japanese Unexamined Patent Application Publication No. 2001-237137 can be mounted on the wiring board at low cost with high reliability without using solder.

Such conventional multilayer ceramic capacitors described above may have lower high-temperature reliability. In particular, a decrease in high-temperature reliability may occur at end portions in the width direction of the internal electrode layers.

Example embodiments of the present invention provide multilayer ceramic capacitors that are each able to reduce or prevent a decrease in high temperature reliability.

A multilayer ceramic capacitor according to an example embodiment of the present invention includes a multilayer body including a plurality of laminated dielectric layers and a plurality of laminated internal electrode layers, a first main surface and a second main surface opposed to each other in a height direction, a first lateral surface and a second lateral surface opposed to each other in a width direction orthogonal or substantially orthogonal to the height direction, a first end surface and a second end surface opposed to each other in a length direction orthogonal or substantially orthogonal to the height direction and the width direction, an effective layer portion including the plurality of dielectric layers and the plurality of internal electrode layers that are alternately laminated, and outer layer portions that sandwich the effective layer portion in the height direction, a first external electrode on the first end surface, and a second external electrode on the second end surface, in which the multilayer body includes an effective layer-width direction-end portion provided at an end portion of the effective layer portion in the width direction and an effective layer-middle portion provided at a middle portion of the effective layer portion, the multilayer body further includes a rare earth segregation region in which a rare earth element is segregated, in a cross section parallel or substantially parallel to the width direction and the height direction, a relationship between a segregation amount of a rare earth element in the rare earth segregation region in the effective layer-width direction-end portion and a segregation amount of a rare earth element in the rare earth segregation region in the effective layer-middle portion is expressed as: the effective layer-middle portion>the effective layer-width direction-end portion, and a dielectric material of the plurality of dielectric layers includes at least one of calcium, zirconium, or strontium, and includes a perovskite-type structure.

According to example embodiments of the present invention, it is possible to provide multilayer ceramic capacitors that are each able to reduce or prevent a decrease in high temperature reliability.

The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings.

Multilayer Ceramic Capacitor

A multilayer ceramic capacitoraccording to an example embodiment of the present invention will be described with reference to the drawings.is an external perspective view of a multilayer ceramic capacitoraccording to an example embodiment of the present invention.is a cross-sectional view taken along the line-of.is a cross-sectional view taken along the line-of.is a cross-sectional view taken along the line-of.is a cross-sectional view taken along the line-of.

As shown in, the multilayer ceramic capacitorhas a rectangular or substantially rectangular parallelepiped shape. The multilayer ceramic capacitorincludes a multilayer bodyhaving a substantially rectangular parallelepiped shape and a pair of external electrodesspaced apart from each other at both end portions of the multilayer body.

In, an arrow T indicates a height direction of the multilayer ceramic capacitorand the multilayer body. The height direction T also refers to a thickness direction and a of lamination (stacking) directionthe multilayer ceramic capacitorand the multilayer body. In, an arrow L indicates a length direction orthogonal or substantially orthogonal to the height direction T of the multilayer ceramic capacitorand the multilayer body. In, an arrow W indicates a width direction orthogonal or substantially orthogonal to the height direction T and the length direction L of the multilayer ceramic capacitorand the multilayer body. The pair of external electrodesis respectively provided at one end and the other end of the multilayer bodyin the length direction L.

The cross section shown inis defined as an LT cross section. The cross section shown inis defined as a WT cross section. The cross section shown inand the cross section shown inare defined as an LW cross sections.

Multilayer Body

Two surfaces of the multilayer bodyopposed to each other in the height direction T are defined as a first main surfaceand a second main surface. Two surfaces opposed to each other in the length direction L orthogonal or substantially orthogonal to the height direction T of the multilayer body are defined as a first end surfaceand a second end surface. Two surfaces opposed to each other in the width direction W orthogonal or substantially orthogonal to the height direction T and the length direction L of the multilayer bodyare defined as a first lateral surfaceand a second lateral surface.

As shown in, the multilayer bodyhas a rectangular or substantially rectangular parallelepiped shape. The length in the length direction L of the multilayer bodymay not be longer than the length in the width direction W. The shapes of the corner portions of the multilayer bodyand the ridge portions of the multilayer bodyare preferably rounded. Each of the corner portions is a portion where the three surfaces of the multilayer body intersect. Each of the ridge portions is a portion where two surfaces of the multilayer body intersect. A portion or the whole of the surface of the multilayer bodymay have unevenness or the like.

The size of the multilayer bodyis not limited. A preferable dimension in the length direction L of the multilayer bodyis about 0.2 mm or more and about 6 mm or less, for example. A preferable dimension in the height direction T of the multilayer bodyis about 0.05 mm or more and about 5 mm or less, for example. The length of the multilayer bodyin the width direction W is preferably about 0.1 mm or more and about 5 mm or less, for example.

Segmentation in Height Direction

As shown in, the multilayer bodyis divided into an inner layer portionand main surface-side outer layer portionsin the height direction T. The main surface-side outer layer portionsinclude a first main surface-side outer layer portionand a second main surface-side outer layer portion. The first main surface-side outer layer portionand the second main surface-side outer layer portionsandwich the inner layer portionin the height direction T. That is, the multilayer bodyis divided into the first main surface-side outer layer portion, the inner layer portion, and the second main surface-side outer layer portion.

Dielectric Layers

The inner layer portionincludes a plurality of dielectric layersand a plurality of internal electrode layersalternately laminated in the height direction T. The inner layer portionincludes the internal electrode layersfrom an internal electrode layerpositioned closest to the first main surfaceto an internal electrode layerpositioned closest to the second main surfacein the height direction T. In the inner layer portion, the plurality of internal electrode layersare opposed to each other with the dielectric layerinterposed therebetween. The inner layer portionis a portion that substantially functions as a capacitor for generating capacitance. The dielectric layersincluded in the inner layer portionare defined as inner dielectric layers. The dielectric layersincluded in the first main surface-side outer layer portionand the dielectric layersincluded in the second main surface-side outer layer portionare each defined as an outer dielectric layer.

The plurality of dielectric layersare made of a dielectric material. The dielectric material includes at least one of calcium, zirconium, or strontium, and includes a perovskite-type structure. More specifically, the dielectric material is a temperature compensating dielectric material with a small rate of change of capacitance with temperature, and includes at least one of calcium, zirconium, or strontium as a main component of the dielectric material. For example, in the dielectric material, at least one calcium or strontium makes up the A site of the perovskite-type structure (ABO), and at least one of zirconium, titanium, or hafnium make ups the B site of the perovskite structure.

Specific examples of the main component of the dielectric material include ceramics including dielectric components such as barium titanate, calcium titanate, strontium titanate, titanium oxide, or calcium zirconate. The multilayer ceramic capacitorof the present example embodiment is a multilayer ceramic capacitor for temperature compensation.

The dielectric material is obtained by adding additives to these main components. Examples of the additive include oxides of manganese, magnesium, dysprosium, or chromium, rare earth elements such as vanadium, samarium, europium, gadolinium, terbium, holmium, erbium, thulium, ytterbium, or yttrium, oxides of cobalt, nickel, lithium, boron, sodium, potassium, or silicon, or glass, in addition to hafnium, silicon, or calcium. Among them, dysprosium and yttrium are preferable as the rare earth elements, for example.

The thickness of each of the dielectric layersis preferably about 0.2 μm or more and about 10 μm or less, for example. The number of the laminated dielectric layersis preferably 15 or more and 1200 or less. The number of layers of the dielectric layeris the sum of the number of the inner dielectric layersand the number of the outer dielectric layers.

Internal Electrode Layer

The plurality of internal electrode layersincludes a plurality of first internal electrode layersand a plurality of second internal electrode layers. The first internal electrode layersand the second internal electrode layersare alternately provided in the height direction T with the dielectric layerinterposed therebetween. The first internal electrode layerseach extend toward the first end surfaceand are exposed at the first end surface. The second internal electrode layerseach extend toward the second end surfaceand are exposed at the second end surface.

As shown in, each of the first internal electrode layersis divided into a first counter portionand a first extension portion. Each of the first counter portionsis opposed to the second internal electrode layerwith the dielectric layerinterposed therebetween. Each of the first extension portionsextends from the first counter portiontoward the first end surface. The first extension portionis exposed at the first end surface.

As shown in, each of the second internal electrode layersis divided into a second counter portionand a second extension portion. Each of the second counter portionsis opposed to the first internal electrode layerwith the dielectric layerinterposed therebetween. The second extension portionextends from the second counter portiontoward the second end surface. The second extension portionis exposed at the second end surface.

In the multilayer ceramic capacitor, the first counter portionand the second counter portionare opposed to each other with the dielectric layerinterposed therebetween, such that a capacitance is generated. With such a configuration, the characteristics of the capacitor are developed in the multilayer ceramic capacitor.

The shape of each of the first counter portionsand the second counter portionsis not limited. A preferable shape of each of the first counter portionsand the second counter portionsis a rectangular or substantially rectangular shape, for example. Similarly, the shape of each of the first extension portionsand the second extension portionsare not limited. A preferable shape of each of the first extension portionsand the second extension portionsis a rectangular shape. In the above-described rectangular shape, each of the rectangular corner portions may have a rounded shape. Each of the rectangular corner portions may have an oblique shape.

The length of each of the first counter portionsin the width direction W and the length of each of the first extension portionin the width direction W may be the same. Either one of the length of each of the first counter portionsin the width direction W and the length of each of the first extension portionsin the width direction W may be short. The length of each of the second counter portionsin the width direction W and the length of each of the second extension portionsin the width direction W may be the same. Either one of the length of each of the second counter portionsin the width direction W and the length of each of the second extension portionsin the width direction W may be short.

Examples of the material of each of the first internal electrode layersand the second internal electrode layersinclude an electrically conductive material such as a metal such as nickel, copper, silver, palladium, or gold, or an alloy including at least one of these metals. When an alloy is used, examples of the material of each of the first internal electrode layersand the second internal electrode layersis an alloy of silver and palladium.

Examples of preferable thicknesses of each of the first internal electrode layersand the second internal electrodes layerare about 0.2 μm or more and about 2.0 μm or less, for example. A preferable number of layers of the sum of the first internal electrode layersand the second internal electrode layersis 15 or more and 1000 or less.

Main Surface-side Outer Layer Portion

As shown in, a portion of an aggregate of the plurality of dielectric layerspositioned between the first main surfaceand the internal electrode layerclosest to the first main surfaceis defined as the first main surface-side outer layer portion. The first main surface-side outer layer portionis adjacent to the first main surfaceof the multilayer body. A portion of an aggregate of the plurality of dielectric layerspositioned between the second main surfaceand the internal electrode layerclosest to the second main surfaceis defined as the second main surface-side outer layer portion. The second main surface-side outer layer portionis adjacent to the second main surfaceof the multilayer body. The dielectric layersof the first main surface-side outer layer portionand the second main surface-side outer layer portionmay be the same or substantially the same as the dielectric layersof the inner layer portion. The material of the inner dielectric layersand the material of the outer dielectric layersmay be the same.

Effective Layer Portion

A portion where the first counter portionof each of the first internal electrode layersand the second counter portionof each of the second internal electrode layersare opposed each other is defined as an effective layer portion. The effective layer portionincludes the dielectric layersand the internal electrode layersthat are alternately laminated. The effective layer portionis a portion of the inner layer portion.each show the range of the effective layer portionin the width direction W and the length direction L. The effective layer portionis a portion of the inner layer portionwithout a side gap described later and an end gap described later. The effective layer portionis also defined as a capacitance generation portion or a capacitor effective portion.

Segmentation in Direction W

The multilayer bodyis divided into a first lateral surface-side outer layer portion, the effective layer portion, and a second lateral surface-side outer layer portionin the width direction W. The first lateral surface-side outer layer portionis a portion including the dielectric layerspositioned between the effective layer portionand the first lateral surface. The second lateral surface-side outer layer portionis a portion including the dielectric layerspositioned between the effective layer portionand the second lateral surface.,, andeach show the ranges of the first lateral surface-side outer layer portion, the effective layer portion, and the second lateral surface-side outer layer portionin the width direction W. The first lateral surface-side outer layer portionand the second lateral surface-side outer layer portionare each defined as a W gap or a side gap.

Segmentation in Length Direction L

The multilayer bodyis divided into a first end surface-side outer layer portion, the effective layer portion, and a second end surface-side outer layer portionin the length direction L. The first end surface-side outer layer portionis a portion including the dielectric layersand the first extension portionspositioned between the effective layer portionand the first end surface. The first end surface-side outer layer portionis an aggregate of portions of the plurality of dielectric layersadjacent to the first end surfaceand the plurality of first extension portions. The second end surface-side outer layer portionis a portion including the dielectric layersand the second extension portionpositioned between the effective layer portionand the second end surface. The second end surface-side outer layer portionis an aggregate of portions of the plurality of dielectric layersadjacent to the second end surfaceand the plurality of second extension portions.,, andeach show the ranges of the first end surface-side outer layer portion, the effective layer portion, and the second end surface-side outer layer portionin the length direction L. The first end surface-side outer layer portionand the second end surface-side outer layer portionare each defined as an L gap or an end gap.

External Electrode

The external electrodesincludes a first external electrodeand a second external electrode. The first external electrodeis an external electrode on the first end surfaceof the multilayer body. The second external electrodeis an external electrode on the second end surfaceside of the multilayer body.

The basic configurations of the first external electrodeand the second external electrodepreferably are the same. The first external electrodeand the second external electrodehave a substantially plane symmetrical shape with respect to the WT cross section at the center in the length direction L of the multilayer ceramic capacitor.

The first external electrodeis on the first end surface. The first external electrodecontacts the first extension portionof each of the plurality of first internal electrode layersexposed at the first end surface. The first external electrodeis electrically connected to each of the plurality of first internal electrode layers. The first external electrodemay also be on a portion of the first main surfaceand a portion of the second main surface, and also on a portion of the first lateral surfaceand a portion of the second lateral surface. In the present example embodiment, the first external electrodeextends from the first end surfaceto a portion of the first main surfaceand a portion of the second main surface, and to a portion of the first lateral surfaceand a portion of the second lateral surface.

The second external electrodeis on the second end surface. The second external electrodecontacts the second extension portionof each of the plurality of second internal electrode layersexposed at the second end surface. The second external electrodeis electrically connected to each of the plurality of second internal electrode layers. The second external electrodemay also be on a portion of the first main surfaceand a portion of the second main surface, and also on a portion of the first lateral surfaceand a portion of the second lateral surface. In the present example embodiment, the second external electrodeextends from the second end surfaceto a portion of the first main surfaceand a portion of the second main surface, and to a portion of the first lateral surfaceand a portion of the second lateral surface.

In the multilayer body, the first counter portionof each of the first internal electrode layersand the second counter portionof each of the second internal electrode layersare opposed to each other with the dielectric layerinterposed therebetween, such that a capacitance is generated. Therefore, the characteristic of the capacitor is developed between the first external electrodeto which the plurality of first internal electrodes layerare connected and the second external electrodeto which the plurality of second internal electrode layersare connected.

Base Electrode Layer